The invention relates to an asynchronous machine with a stator and a squirrel-cage rotor, the squirrel-cage rotor having a shaft and a laminate stack, and rotor bars being located in the laminate stack, which rotor bars are guided at both ends of the laminate stack through the openings of in each case one end plate and are terminated with a short-circuiting ring, which electrically conductively connects the ends of the rotor bars of one side of the squirrel-cage rotor.
Electrical machines are used in a very large number of technical fields. With electrical machines it is necessary to distinguish between DC machines, AC machines and three-phase machines. Three-phase machines can be split into three-phase synchronous machines and three-phase asynchronous machines.
All of these electrical machines contain, inter alia, a stator at rest and a rotor which is mounted such that it is capable of rotating. The rotor is fitted with a winding system, depending on the design. This winding system may comprise one or more wire windings or bar windings. Squirrel-cage windings can also be constructed from wire windings or else bar windings. In the case of bars and squirrel-cage windings in asynchronous motors, the result is a squirrel-cage rotor. In this case, the laminate stack of the rotor contains rotor bars, which are conductively connected to one another at their ends by means of short-circuiting rings.
It is known that the transition region between the rotor bars and the short-circuiting rings is subjected to shear stress when the rotor is heated during operation, so that breakage of the joint may occur. This is primarily because of the different expansion of the rotor laminate stack and the short-circuiting rings during heating and centrifugal forces during operation. The document JP 2000-014105-A therefore proposes designing the ends of the rotor bars and the short-circuiting rings in such a way that they are reinforced, so that the rotor bars and the short-circuiting rings have a greater cross-sectional area in common. Furthermore, it is also known from the document EP 1 453 180 A2 to guide the rotor bars on each side through an end plate before the short-circuiting ring is joined.
However, one disadvantage is the fact that although the risk of breakage of a joint between a rotor bar and a short-circuiting ring is reduced, a breakage can still nevertheless occur.